Permanent magnet core instrument with flattened yoke



May 17, 1966 D. sTAHLY ETAL 3,252,092

PERMANENT MAGNET E INSTRUMENT WITH FLATTENED YOKE FRICTIONALLY SUPPORTING A FLAT SIDED CORE Filed Dec. 22, 1961 ATTRNEYS.

United States Patent O `PERMANENT MAGNET CORE INSTRUMENT WITH FLATTENED YOKE FRICTIONALLY SUPPORT- ING A FLAT SIDED CORE' Daniel C. Stahly, Villa Park, and Frederick M. Bender,

Mount Prospect, Ill., assignors to Sun Electric Corporation, Chicago, Ill., a corporation of Illinois Filed Dec. 22, 1961, Ser. No. 161,601 2 Claims. (Cl. 324-151) pieces to hold them in assembled position. Such frame plates have also provided bridging members at the ends of the yoke on which the instrument coil is pivoted. The assembly of structures of this type is a diicult and time consuming task because of the large number of parts to be handled and the necessity vof laccurately positioning the parts relative to each other.

It is accordingly an object of the present invention to provide a core magnet instrument which is so constructed as to require a minimum number of parts and to be assembled easily and accurately.

According to a feature of the invention, the magnet and pole pieces are held accurately positioned in the yoke by a unitary nonmagnetic frame, preferably formed of die cast metal and which also provides integral bridges to carry bearings for mounting the coil. The frame preferably has opposed flat sides formed with inwardly extending projections thereon to engage and locate the magnet and pole pieces, which sides are initially spread so that the magnet and pole pieces can easily be inserted between them and which are pressed together by the yoke when assembled therein.

The above and other objects and features of the inven- Ation will be m-ore readily apparent from the following description when read in connection with the accompanying drawing, in which:

FIGURE 1 is a top plan view of a core 4magnet construction embodying the invention;

FIGURE 2 is a top plan view of the frame with parts broken away and in section illustrating the initial condition thereof;

FIGURE 3 is a section on the line 3-3 of FIGUREv 1;

FIGURE 4 is a disassembled perspective view; and

FIGURE 5 is acentral section through the frame.

The complete core magnet instrument, as best seen in FIGURES 1 and 3, comprises a yoke 10 of magnetic material having at opposed sides 11 joined by arcuate ends 12. The yoke is made of a magnetic material, such as soft iron, and may be one piece, as shown, or of laminar construction.

A core magnet 13 is mounted in the yoke and is of smaller size than the yoke to be spaced from the internal walls thereof. The core magnet has flat opposed sides 14 joined by arcuately curved ends 15. Arcuate pole pieces 16 fit over the arcuate ends 15 of the magnet and terminate in flattened ends in the planes of the flat magnet sides 14. The assembly of magnet and pole pieces is shorter than the yoke so that when the assembly is positioned in the yoke arcuate space will be left between the ends of the magnet and the ends of the yoke in which the instrument coil can move.

The magnet and pole pieces. are held a-ssembled in the yoke by a unitary frame of non-magnetic material which is preferably die cast metal, although other materials could be employed. The frame is formed with a pair of 3,252,092 Patented May 17, 1966 spaced flat sides 17 of a size to overlie the sides of the magnet and the ends of the pole pieces and to lit between the flat sides 14 of the magnet and the at sides 11 of the yoke. Each of the sides, as best seen in FIGURE 5, is formed with an upper flange 18-which preferably projects outwardly from the-sides partially to overlie the top surface of the yoke and which extends inwardly a short distance from the -sides to provide `a stop engaging the upper surface of the magnet and the pole pieces. A similar iange or shoulder 19 is formed at the bottom of each of the sides 17 and projects inwardly therefrom to engage the lower ends of the magnet and pole pieces. The magnet and pole pieces are thus held against vertical movement between the flanges 18 and 19.

' The sides are joined by a U-shaped lower bridge piece 21 which extends downwardly from the lower edge of each of the sides centrally of its width and which includes a bar or strap 22 extending between the sides spaced outwardly from the lower edges thereof. The bar or strap 22 is formed centrally of its length with an opening 23 therein to receive and support a bearing 24, as shown in FIGURE 3. At the upper end the arms are joined at one side only thereof by an arcuate llange 25 which forms a continuation of the anges 18 and which in the assembly overlie one arcuate end portion 12 of the yoke.

l A bridge arm 26 is formed integrally with the flange 25 projecting upward therefrom and then over the central portion of the yoke where it is formed with an opening 27 for mounting a bearing 28, as shown in FIGURE 3.

The frame is initially formed, as shown in FIGURE 2,

with its sides diverging away from the flange 25. The sides are formed adjacent to the flange 25 with inwardly extending stop projections 29 which will engage the adjacent end portions of the pole pieces and limit movement thereof in one direction between the arms. Initially the offset ends of the -sides are straight so that they can be cast and pulled from the mold, but after they have been yremoved from the mold short inwardly extending projections 31 are struck 4up therefrom as, for example, by striking the ends of the sides near the inner surfaces thereof with a chisel point. Due to spreading of the sides in their initial position the magnet 13 and pole pieces 16 can be slipped between the projections 31, as shown in FIGURE 2, until one of the pole pieces engages the stop projections 29. When the frame is insertedin the yoke, the sides 17 thereof will be squeezed together into engagement with the sides of the magnet and the ends of the pole pieces and to cause the projections 31 to extend over and engage the adjacent curved face of the other1 pole piece. In this way, when the magnet, pole pieces and frame are assembled in the yoke the magnet and pole pieces will be securely and accurately positioned relative to each other and will be held in the frame against movement in any direction.

The assembly is completed by a generally rectangular coil 32 having short stub shafts 33 at its opposite ends which engage the bearings 24 and 28 in the bridge pieces to support the coil pivotally. It will be noted that the two side legs of the coil pass over the arcuate ends 15 of the magnet and can swing in the arcuate spaces 20 between the pole pieces and the ends of the yoke. It

' then be adjusted to support the eoil pivotally after which the frame, coil and magnet and pole piece `assembly may be inserted endwise into the yoke until the flange' 18 and 25 rest against the upper surface of the yoke. The assembly may be completed by inserting fastenings, such as machine screws 35, through openings in the flange Z5 into threaded openings in the end of the yoke. This completes the assembly with all of the parts accurately and securely held relative toeach other. The completed assembly -may be mounted either from the bottom bridge piece 21 or from the bottom of the yoke, as desired.

While one embodiment of the invention has Abeen shown and described herein, it will be understood that it is illustrative only and not to betaken as a deinition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

-1. A Vcore magnet instrument comprising a tubular yoke of magnetic material having v'opposed flat sides and arcurately curved'ends, a frame of non-magnetic material having spaced flat sides iitting into the yoke against the flat sides thereof, a magnetrhaving flat sides fitting against vthe flat frame sides and arcuately curved ends spaced from the -arcuately curved ends of the yoke, bridge members integrally formed on the frame and centrally overlying opposite ends `of the yoke, inwardly extending projections on the sides of the frame engaging the magnet to locate itand holdvit in position, the sides of the frame Vbeing initially vflared for insertion of the magnet past the projections and being pressed together' into engagement with the magnet by the yoke, and a `coil pivoted von the bridge members and having 'two legs extending Vthrough the spaces between the ends of the magnet and the ends of the yoke.

2. A core magnet instrument comprising a tubular yoke of magnetic material having opposed tiat sides and arcuately curved ends, a frame of non-magnetic material having spaced flat sides itting into the yoke against the flat sides thereof, a magnet having iiat sides litting against the tiat frame `sides and arcuately curved ends spaced from the Iarcuately curved ends of the yoke, a U-shaped bridge member spanning the frame sides at one end of the frame, a ange connecting the frame sides at theother end thereof and overlying a ycurved end of the yoke, a bridge arm extending from the flange centrally over the center portion of the yoke, vinwardly extending projections on the frame sides engaging and locating the magnet, the frame sides initially being spread apart so that the magnet can be inserted between them and being pressed together by the yoke sides to bring the inwardly extending projections into engagement with the magnet, 'and a coil pivoted on the bridge member and bridge arm and having two legs Aextending respectively through the spaces' between the ends of the magnet andthe ends of the yoke.

References Cited lby the Examiner UNITED STATES PATENTS 2,840,767 6/1958 Ammon 324-151 2,978,640 4/ 1961 Arbeiter 324-151 WALTER L. CARLSON, Primary Examiner.

v FREDERICK M. STRADER, Examiner.

R. V. ROLINEC, Assistant Examiner. 

1. A CORE MAGNET INSTRUMENT COMPRISING A TUBULAR YOKE OF MAGNETIC MATERIAL HAVING OPPOSED FLAT SIDES AND ARCUATELY CURVED ENDS, A FRAME OF NON-MAGNETIC MATERIAL HAVING SPACED FLAT SIDES FITTING INTO THE YOKE AGAINST THE FLAT SIDES THEREOF, A MAGNET HAVING FLAT SIDES FITTING AGAINST THE FLAT FRAME SIDES AND ARCUATELY CURVED ENDS SPACED FROM THE ARCUATELY CURVED ENDS OF THE YOKE, BRIDGE MEMBERS INTEGRALLY FORMED ON THE FRAME AND CENTRALLY OVERLYING OPPOSITE ENDS OF THE YOKE, INWARDLY EXTENDING PROJECTIONS ON THE SIDES OF THE FRAME ENGAGING THE MAGNET TO LOCATE IT AND HOLD IT IN POSITION, THE SIDES OF THE FRAME BEING INITIALLY FLARED FOR INSERTION OF THE MAGNET PAST THE 